Auto Electronics

Freescale technology drives two-mode GM hybrids

Freescale is providing microcontroller technology for the drive train used in General Motors’ hybrid full-size SUVs, the Chevy Tahoe Hybrid and GMC Yukon Hybrid.

Freescale has supplied technology for GM electronic control systems since 1979, and in 2004 GM said it plans to use Freescale 32-bit Power Architecture MCUs in its powertrain engine control systems around the world. Freescale currently leads the market in powertrain MCUs, with a market share of nearly 50%.

Based on the GM-Allison hybrid system for city buses, the patented hybrid technology employed in the Tahoe and Yukon hybrids is equally optimized for city and highway driving, unlike current production hybrid systems, which generally are optimized for city driving.

The Tahoe and Yukon hybrids feature two electric motors, and propulsion modes that optimize for city or highway driving. For low speed driving with light loads, the vehicles can operate on electric power, engine power, or a combination of both. The second mode, for higher-speed operation, provides an electric assist when needed. The uninterrupted blending of power between the electric motor and gasoline or diesel engine is controlled by the powertrain control units and software that monitors driving and selects the proper transmission mode. Freescale MCUs are used in the power inverter module.

“This is a step up in complexity for hybrid transmission control,” noted Kevin Klein, Freescale’s automotive microcontroller marketing manager.

GM said the two-mode hybrid transmission boosts the fuel economy of the SUVs and large luxury vehicles by up to 50% in city driving compared to traditional gasoline engines. The models also feature a 6,000-pound towing capacity.
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